JP2009062438A - Rubber composition for tire tread - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for tire tread, which exhibits excellent low-fuel consumption and excellent strength properties such as tensile property and abrasion resistance, and can enhance yield by improvement of tensile elongation after vulcanization. <P>SOLUTION: The rubber composition for tire tread is obtained by blending 100 pts.wt. of diene rubber containing ≥50 wt.% of natural rubber with: 30-150 pts.wt. of a reinforcing filler containing ≥20 pts.wt. of a carbon black having a cetyltrimethylammonium bromide adsorption specific surface area of 110-180 m<SP>2</SP>/g; and 0.5-10 pts.wt. of a polyether polyol. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rubber composition for a tire tread, and more specifically, exhibits excellent fuel economy and strength properties such as tensile properties and wear resistance when used as a tire tread, and further exhibits elongation at break after vulcanization. It is related with the rubber composition for tire tread which can improve a yield by improvement of this.

  In order to meet the social demands for energy saving, in recent years, the development of fuel-efficient tires has been actively carried out in the tire industry, and end-modified polymers and fuel-efficient carbon black are blended into rubber compositions. For example, Patent Documents 1 and 2 below have proposed to improve fuel economy by doing this, but when such a compounding agent is used, the wear resistance is insufficient when used as a tire tread. Problem, because the elongation at break of the rubber composition after vulcanization is reduced, part of the tread fits into the mold and breaks into a block shape when taken out from the mold after the vulcanization molding process at the time of tire manufacture There is a tendency that the yield is poor.

  On the other hand, in order to enhance the dispersibility of silica and / or carbon black as a reinforcing filler for the rubber component, it has been proposed, for example, in Patent Documents 3 to 7 below to add processability and processability. Although certain effects have been achieved with respect to improvement in strength properties such as rupture strength and abrasion resistance after vulcanization, improvement in rupture resistance and fuel efficiency has not been studied.

JP 2004-059740 A JP-A 63-264647 JP-A-9-118786 Japanese Patent Laid-Open No. 11-343366 JP 2002-88193 A JP 2001-288299 A JP 2005-343963 A

  Therefore, the present invention exhibits excellent fuel economy and strength properties such as tensile properties and wear resistance when used as a tire tread, and further improves the yield during tire production by improving the elongation at break after vulcanization. An object of the present invention is to provide a rubber composition for a tire tread.

  As a result of diligent research to solve the above-mentioned problems, the present inventors have added a specific amount of the following general formula (I) to a rubber composition containing a diene rubber containing 50% by weight or more of natural rubber and silica.

(Wherein, l, m and n each independently represents an integer of 2 to 10)
When used as a tire tread after vulcanization, it exhibits excellent fuel economy, strength properties such as tensile properties and abrasion resistance, and elongation at break after vulcanization. As a result of the improvement, it was found that the yield at the time of taking out from the mold after the vulcanization molding process at the time of tire production can be increased, and the present invention has been completed.

That is, according to the present invention, 20 parts by weight or more of carbon black having a cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of 110 to 180 m ² / g per 100 parts by weight of diene rubber containing 50% by weight or more of natural rubber. 30 to 150 parts by weight of reinforcing filler containing, and the following general formula (I):

(Wherein, l, m and n each independently represents an integer of 2 to 10)
The rubber composition for tire treads characterized by including 0.5 to 10 parts by weight of a polyether polyol represented by the formula (1) is provided.

  The diene rubber used in the rubber composition of the present invention contains 50% by weight or more of natural rubber (NR) based on the total amount from the viewpoint of wear resistance and low fuel consumption required for a tire tread. In addition to natural rubber, styrene-butadiene copolymer rubber (SBR), butadiene rubber (BR), polyisoprene rubber (IR), butyl rubber (IIR), nitrile rubber (NBR), chloroprene rubber (CR), ethylene -One or more diene rubbers selected from propylene-diene copolymer rubber (EPDM) and the like may be included.

  As long as the reinforcing filler compounded in the rubber composition of the present invention contains carbon black having the above CTAB adsorption specific surface area in the above compounding ratio, it is known as a reinforcing filler for rubber compositions. One or more fillers may be included. The compounding amount of the reinforcing filler is 30 to 150 parts by weight with respect to 100 parts by weight of the diene rubber. If the blending amount of the filler is less than 30 parts by weight, the rubber cannot be sufficiently reinforced, so that there is a risk that strength properties such as wear resistance and elongation at break of the rubber composition may be lowered. There is a possibility that the rubber composition at the time of kneading becomes too hard and the processability is lowered.

  As reinforcing fillers other than carbon black, for example, metal oxides such as silica, diatomaceous earth, alumina, titanium oxide, metal carbonates such as calcium carbonate, magnesium carbonate, dawsonite and hydrotalcite, such as talc, kaolin, clay, Examples thereof include metal silicates such as mica, montmorillonite, bentonite, activated clay, sepiolite, imogolite, sericite, and glass fiber, and carbon allotropes and carbon compounds such as graphite, carbon fiber, and fullerene. As the reinforcing filler other than carbon black, silica is preferable from the viewpoint of reinforcing properties.

Carbon black can be appropriately selected from those generally used in the rubber industry as long as it has a CTAB adsorption specific surface area of 110 to 180 m ² / g, and is not limited to its production method. If the CTAB adsorption specific surface area of the carbon black is less than 110 m ² / g, the reinforcing property is not sufficient, and if the CTAB adsorption specific surface area exceeds 180 m ² / g, the dispersibility of the carbon black deteriorates. In the description of the present specification, “CTAB adsorption specific surface area” means a specific surface area (unit m ² / g) measured according to JIS K6217. Carbon black is blended in an amount of 20 parts by weight or more, preferably 40 parts by weight or more with respect to 100 parts by weight of the diene rubber.

  The shape of the reinforcing filler is not particularly limited, and may be a fiber shape, a needle shape, a plate shape, a spherical shape, a granular shape, a balloon shape, or an indefinite shape. Further, the reinforcing filler may be surface-treated with a treating agent as necessary, provided that the effect of the polyether polyol of the general formula (I) is not hindered.

  The polyether polyol represented by the above general formula (I) blended in the rubber composition of the present invention is 0.5 to 10 parts by weight, preferably 4.0 to 8.0 parts per 100 parts by weight of the diene rubber. Blended in parts by weight. If the blending amount of the polyether polyol is less than 0.5 parts by weight with respect to 100 parts by weight of the diene rubber, the effect of improving the physical properties of the rubber composition is small, and if it exceeds 10 parts by weight, scorch tends to occur. In addition, there is a problem that the elastic modulus and wear resistance after vulcanization are lowered. Moreover, when l, m, and n exceed 10, the measurement workability of the polyether polyol is lowered.

  In addition to the reinforcing filler and polyether polyol described above, the rubber composition of the present invention may optionally contain any compounding agent commonly used in the rubber industry, such as a vulcanization accelerator, Sulfur agents, scorch inhibitors, ultraviolet absorbers, processing aids, anti-aging agents, and the like can also be added as appropriate in general amounts. In mixing the additive, a general method is used as a method of mixing. Generally, a lump, pellet, or powdery component is mixed with an appropriate mixer such as a kneader, an internal mixer, or a Banbury mixer. A method of pressure molding after mixing using a roll or the like can be applied.

  The order of addition of each component during kneading is not particularly limited. Even if the polyether polyol is mixed with the reinforcing filler in advance and then blended with the rubber, the polyether polyol, the reinforcing filler and the rubber are blended simultaneously. May be.

  The present invention will be described in more detail with reference to the following examples and comparative examples, but it goes without saying that the technical scope of the present invention is not limited by these examples.

Preparation of rubber compositions of Comparative Examples 1 and 2 and Examples 1 and 2 In accordance with the composition shown in Table 1 below, using a 1.7 liter closed Banbury mixer, natural rubber, silica, carbon black, zinc oxide and the like were added. Materials other than the sulfur-based material were mixed for 5 minutes, discharged from a mixer at 150 ° C., and then cooled to room temperature. Thereafter, the mixture was mixed again for 5 minutes using a 1.7 liter closed-type Banbury mixer, released at 150 ° C., and then mixed with a vulcanization accelerator and sulfur using an open roll, and Comparative Examples 1-2 and Examples 1 to 2 were mixed. 2 unvulcanized rubber compositions were obtained.

Test Methods The performance of the rubber compositions obtained in the following examples and comparative examples was determined by the following test methods. The results of each test are as shown in Table 1.
(1) Low fuel consumption The unvulcanized rubber compositions of Comparative Examples 1-2 and Examples 1-2 were press vulcanized at 150 ° C for 30 minutes to produce a vulcanized rubber sheet having a thickness of 2.0 mm. A test piece was prepared from this vulcanized rubber sheet, and loss tangent was measured using a viscoelasticity spectrometer manufactured by Toyo Seiki Seisakusho under the conditions of strain 10 ± 2%, frequency 20 Hz, and ambient temperature 60 ° C. in accordance with JIS K6394. Tan δ (60 ° C.) was determined. The test results were expressed as an index with the value of tan δ (60 ° C.) obtained for Comparative Example 1 being 100. The larger the index value, the more the exothermic property is reduced.

(2) Tensile stress Each unvulcanized rubber composition of Comparative Examples 1-2 and Examples 1-2 was press vulcanized at 150 ° C. for 30 minutes to produce a vulcanized rubber sheet having a thickness of 2.0 mm. A JIS No. 3 dumbbell specimen was punched from the obtained vulcanized rubber sheet. Next, the tensile stress was measured about the test piece of each example based on JISK6251. The measurement results were expressed as an index with the measurement value of Comparative Example 1 as 100. The larger the index value, the greater the tensile stress and the higher the reinforcement.

(3) Elongation at break Each unvulcanized rubber composition of Comparative Examples 1-2 and Examples 1-2 was press vulcanized at 150 ° C. for 30 minutes to produce a vulcanized rubber sheet having a thickness of 2.0 mm. A JIS No. 3 dumbbell specimen was punched from the obtained vulcanized rubber sheet. Next, about the test piece of each example, the breaking elongation was measured based on JISK6251. The measurement results were expressed as an index with the elongation at break of Comparative Example 1 as 100. The larger the index value, the greater the elongation at break.

(4) Abrasion resistance In accordance with JIS K6264, the wear amount of Comparative Example 1 was measured by measuring the amount of wear under the condition of a slip rate of 25% using a lambone wear tester (manufactured by Iwamoto Seisakusho Co., Ltd.). The amount of wear determined in Comparative Example 2 and Examples 1 and 2 was expressed as a relative value with respect to 100. It represents that it is excellent in abrasion resistance, so that a relative value is large.

  From the results shown in Table 1, when the polyether polyol represented by the general formula (I) is added to the rubber composition in the predetermined amount, the tensile stress, elongation at break, wear resistance and fuel consumption are balanced after vulcanization. It turns out that it improves well.

Claims (1)

30 to 150 parts by weight of a reinforcing filler containing 20 parts by weight or more of carbon black having a cetyltrimethylammonium bromide adsorption specific surface area of 110 to 180 m ² / g with respect to 100 parts by weight of a diene rubber containing 50% by weight or more of natural rubber The following general formula (I):

(Wherein, l, m and n each independently represents an integer of 2 to 10)
A rubber composition for a tire tread, comprising 0.5 to 10 parts by weight of a polyether polyol represented by the formula: